Pension plans 4 (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the beginning of the year	$ 0	$ 2.7
Actual return on plan assets	0	(0.1)
Purchases, sales and settlments, net	0	(2.5)
Transfer into (out of) Level 3		(0.1)
Foreign currency exchange rates	0	0
Fair value of plan assets at the end of the year	0	0
General insurance account [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the beginning of the year	19.0	19.1
Actual return on plan assets	1.0	0.8
Purchases, sales and settlments, net	(3.2)	(1.2)
Transfer into (out of) Level 3		0
Foreign currency exchange rates	0.8	0.3
Fair value of plan assets at the end of the year	17.6	19.0
U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the beginning of the year	555.3	481.4
Actual return on plan assets	65.2	68.6
Foreign currency exchange rates	0	0
Fair value of plan assets at the end of the year	627.2	555.3
U.S. Pension Plans [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	213.0	293.6
U.S. Pension Plans [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	414.2	261.6
U.S. Pension Plans [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	5.9	4.0
U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	9.8	10.4
U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	199.2	123.1
U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	2.7	2.2
U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	45.6	19.1
U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	194.2	265.0
U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	17.5	19.7
U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	10.2	22.4
U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	133.3	74.5
U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	8.8	14.8
U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | General insurance account [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | General insurance account [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
U.S. Pension Plans [Member] | General insurance account [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the beginning of the year	63.3	58.7
Actual return on plan assets	5.5	4.3
Foreign currency exchange rates	1.5	2.1
Fair value of plan assets at the end of the year	67.2	63.3
Non-U.S. Pension Plans [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	44.8	39.9
Non-U.S. Pension Plans [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	4.8	4.4
Non-U.S. Pension Plans [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	17.6	19.0
Non-U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	44.8	39.9
Non-U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	4.8	4.4
Non-U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | General insurance account [Member] | (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | General insurance account [Member] | (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	0	0
Non-U.S. Pension Plans [Member] | General insurance account [Member] | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at the end of the year	$ 17.6	$ 19.0